Automated Dependent Surveillance-Broadcast, or ADS-B, is the future of Air Traffic Control. It's an automated system that allows hardware on planes to radio in the aircraft's coordinates to the tower, instead of using radar to pick up each plan individually. Problem is, you can hack it to hell
While the ADS-B is safeguarded against more traditional digital worries—like being totally shut down or unable to communicate with planes—it lacks the encryption and authentication to protect it from other forms of attack. For example, "a medium-technical savvy person" could easily impersonate a plane. Someone who knows what they're doing? They could impersonate thousands.